Process for producing dispersion liquid of intrinsic electroconductive polymer in organic solvent

ABSTRACT

This invention provides a process for producing a dispersion liquid of an intrinsic electroconductive polymer in an organic solvent, comprising a deionization step of deionizing an aqueous colloid dispersion liquid of an intrinsic electroconductive polymer by a liquid feeding method to remove cations adsorbed on the intrinsic electroconductive polymer, a solvent displacement step of subjecting water in the aqueous colloid dispersion liquid after the deionization step to solvent displacement with an organic solvent (excluding N-methylpyrrolidone and dimethyl sulfoxide), and an additive treatment step of, after the solvent displacement step, adding N-methylpyrrolidone or dimethyl sulfoxide. This process can easily produce a dispersion liquid of an intrinsic electroconductive polymer in an organic solvent that can be used in various applications such as electrode materials, antistatic agents, ultraviolet absorbers, heat absorbers, electromagnetic wave absorbers, sensors, electrolytes for electrolytic capacitors, and electrodes for rechargeable batteries.

TECHNICAL FIELD

The present invention relates to a method for production of organicsolvent dispersion of intrinsically conductive polymer.

BACKGROUND ART

Aromatic conductive polymers, such as polyaniline, polythiophene, andpolypyrrole, seem useful because of their good stability and highconductivity but they are limited in the field of application because oftheir poor processability due to insolubility in organic solvents.

According to a recent report, it is possible to improve processabilityby dispersing the conductive polymer into water or an organic solventsuch as aromatic solvent. (See Patent Document Nos. 1 and 2.)

Making the above-mentioned conductive polymer into a dispersion involvesits conversion into an intrinsically conductive polymer by addition of adopant and subsequent dispersion in water or a mixture of water andhydrophilic solvent. However, the complexity of these steps prevents theconductive polymer from being used in the form of coating material.

One way proposed to address this problem is by solvent substitution.(See Patent Document Nos. 3 and 4.) The method disclosed in PatentDocument No. 3 is very complex because solvent substitution needsvigorous stirring.

There is a simple method for solvent substitution that involvesdeionization with an ion-exchange material. This method, however, isincapable of removing cations strongly adhered to the surface ofparticles of intrinsically conductive polymer, and hence it merely givesan unstable dispersion (with a water content no less than 1 wt %) ofintrinsically conductive polymer in an organic solvent. (See PatentDocument No. 4.)

The above-mentioned problems encountered in the prior art technologyhave to be solved to enlarge the application field of the conductivepolymer, and hence there is a demand for a simple method for preparingan organic solvent dispersion of an intrinsically conductive polymer.

[Patent Document 1] JP-A-H7-90060

[Patent Document 2] JP-A-H2-500918

[Patent Document 3] JP-A-2004-532292

[Patent Document 4] JP-A-2004-532298

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The present invention was completed in view of the foregoing. It is anobject of the present invention to provide a simple method for producingan organic solvent dispersion of an intrinsically conductive polymerwhich can be applied to various uses as electrode materials, antistaticagents, UV light absorbers, heat ray absorbers, electromagnetic waveabsorbers, sensors, electrolyte for electrolytic capacitors, andelectrodes for secondary batteries.

Means for Solving the Problems

In order to solve the above-mentioned problems, the present inventorcarried out a series of investigations, which led to the finding thatdispersion of an intrinsically conductive polymer into an organicsolvent is possible if its aqueous colloidal dispersion undergoesdeionization by a passing of liquid and subsequent solvent substitution(International Patent Application No. PCT/JP2006/302326).

Based on the above method, the inventor made further studies on animprovement thereof and, as a result, found that when a specificadditive is added after the solvent substitution, a thin film obtainedfrom the resulting organic solvent dispersion of an intrinsicallyconductive polymer is increased in conductivity, thereby accomplishingthe invention.

The present invention is directed to the following aspects (1) to (22).

(1) A method for producing an organic solvent dispersion of anintrinsically conductive polymer, which includes:

a deionizing step of deionizing an aqueous colloidal dispersion of anintrinsically conductive polymer by the passing of liquid, therebyclearing the intrinsically conductive polymer of cations adheringthereto;

a solvent substitution step of substituting water in the aqueouscolloidal dispersion with an organic solvent except forN-methylpyrrolidone and dimethylsulfoxide after the deionizing step; and

an additive-treating step of adding N-methylpyrrolidone ordimethylsulfoxide to the dispersion obtained by the solvent substitutionstep.

(2) The method of 1 above, wherein an amount of the N-methylpyrrolidoneor dimethylsulfoxide ranges from 0.01 to 5.00% (W/V) relative to thetotal volume of the organic solvent dispersion.(3) The method of 2 above, wherein the amount of the N-methylpyrrolidoneor dimethylsulfoxide ranges from 0.01 to 0.99% (W/V) relative to thetotal volume of the organic solvent dispersion.(4) The method of 1 above, wherein the deionizing step is accomplishedby ion exchange.(5) The method of 1, further including a filtration step of subjectingthe aqueous colloidal dispersion of an intrinsically conductive polymerto ultrafiltration before the deionizing step.(6) The method of 1 above, wherein the solvent substitution step isaccomplished in such a way as to keep a solid contents in a range of0.05 to 10.0 wt %.(7) The method of 1 above, wherein the solvent substitution step isaccomplished in such a way as to reduce a water content below 1%.(8) The method of 1 above, wherein the solvent substitution step isaccomplished by slowly adding the organic solvent to the aqueouscolloidal dispersion, thereby removing water.(9) The method of 1 above, wherein the organic solvent is an alcoholhaving 1 to 3 carbon atoms.(10) The method of 1 above, wherein the organic solvent has a boilingpoint of not higher than 80° C.(11) The method of 1, wherein the intrinsically conductive polymercontains at least an aniline unit.(12) The method of 1, wherein the intrinsically conductive polymer isdoped polyaniline, doped polythiophene, a mixture thereof or a copolymerthereof.(13) An organic solvent dispersion of an intrinsically conductivepolymer obtained by the method defined in any one of 1 to 12 above.(14) A dispersion of an intrinsically conductive polymer in an organicsolvent except for N-methylpyrrolidone and dimethylsulfoxide, whichincluding N-methylpyrrolidone or dimethylsulfoxide, a water contentbeing less than 1%.(15) The dispersion of 14 above, wherein a content of theN-methylpyrrolidone or dimethylsulfoxide ranges from 0.01 to 5.00% (W/V)relative to the total volume of the organic solvent dispersion.(16) The dispersion of 15 above, wherein the content of theN-methylpyrrolidone or dimethylsulfoxide ranges from 0.01 to 0.99% (W/V)relative to the total volume of the organic solvent dispersion.(17) The dispersion of 14 above, wherein the organic solvent is analcohol having 1 to 3 carbon atoms.(18) The dispersion of 14 above, wherein the organic solvent has aboiling point of not higher than 80° C.(19) The dispersion of 14 above, wherein the intrinsically conductivepolymer has at least an aniline unit.(20) The dispersion of 14 above, wherein the intrinsically conductivepolymer is a doped polyaniline, a doped polythiophene, a mixture thereofor a copolymer thereof.(21) The dispersion of 14 above, wherein the conductive polymer is amixture of a doped polyaniline and a doped polythiophene, or a copolymerthereof.(22) The dispersion of 14 above, wherein the intrinsically conductivepolymer is a mixture of a doped polyaniline and a doped polythiophene.

EFFECT OF THE INVENTION

The method according to the present invention permits easy production ofan organic solvent dispersion of an intrinsically conductive polymer,with its water content reduced below 1%.

Since certain types of additives are contained in the organic solventdispersion of an intrinsically conductive polymer of the invention, athin film or the like prepared from this dispersion exhibits excellentconductivity.

The organic solvent dispersion of an intrinsically conductive polymerwhich is produced by the method of the present invention has a simplecomposition and finds use as a coating material which gives a thin filmhaving such properties as electrical conductivity and/or absorption ofheat rays (infrared rays) characteristic of intrinsically conductivepolymers. Therefore it will find use in broad application fieldsincluding electrode material, antistatic agent, UV light absorber, heatray absorber, electromagnetic wave absorber, sensors, electrolyte forelectrolytic capacitors, and electrodes for secondary batteries. Thusthe present invention will enlarge the application fields of conductivepolymers.

BEST MODE FOR CARRYING OUT THE INVENTION

A detailed description of the invention will be given in the following.

The method for producing an organic solvent dispersion of anintrinsically conductive polymer according to the invention includes adeionizing step of deionizing an aqueous colloidal dispersion of anintrinsically conductive polymer by the passing of liquid, therebyclearing the intrinsically conductive polymer of cations adheringthereto, a solvent substitution step of substituting water in theaqueous colloidal dispersion with an organic solvent after thedeionizing step, and an additive-treating step of addingN-methylpyrrolidone or dimethylsulfoxide to the dispersion obtained bythe solvent substitution step.

The term “intrinsically conductive polymer” as used in the presentinvention denotes those polymers which are in the form of polyradicalcationic salt or polyradical anionic salt that result from doping andhence which exhibit electrical conductivity by themselves.

Intrinsically conductive polymers suitable for the present invention arenot specifically restricted; they include any known polymers in dopedform of aniline, pyrrole, thiophene, acetylene, etc., and derivativesthereof. It will be noted that although they may be used alone or incombination with one another, it is preferred to use polymers part ofwhich contains at least an aniline unit. The dopants for theintrinsically conductive polymers are exemplified by sulfonic acids(such as polystyrenesulfonic acid, methanesulfonic acid,alkylbenzenesulfonic acid, and camphor sulfonic acid), carboxylic acids(such as acetic acid), hydrogen halides (such as hydrochloric acid, andhydrobromic acid).

Desirable samples of the intrinsically conductive polymer may beprepared by the method disclosed in JP-A-H7-90060 and JP-A-H2-500918.Polythiophene (typically (3,4-ethylenedioxythiophene), polyaniline, amixture thereof and a copolymer thereof, which are commerciallyavailable in the form of aqueous colloidal dispersion, are alsodesirable. The polyaniline, a mixture of polyaniline and polythiophen ora copolymer thereof are most suitable because their aqueous colloidaldispersion are composed of very small particles.

The aqueous colloidal dispersion of the intrinsically conductive polymercontains a large amount of free ions originating from excess dopant(such as sulfonic acid) and also free ions (such as ammonium ions,potassium ions, sulfate ions, etc.) originating from decompositionproducts of salts (such as ammonium persulfate and potassium persulfate)used for production. Also, such cations as ammonium ions and potassiumions are strongly adhered to the dopant portion of the particles of theintrinsically conductive polymer in the dispersion.

Consequently, it is necessary to remove these free ions and excessdopant before the intrinsically conductive polymer is dispersed into anorganic solvent so that they will not adversely affect stabledispersion.

[Deionizing Step]

The present invention involves a deionizing step which is intended toremove free ions, excess dopant, and cations adhering to theintrinsically conductive polymer.

A method for deionization is not specifically restricted so long as itcan remove cations adhering to the intrinsically conductive polymer.However, ion exchange is a preferred method for deionization because iteffectively removes cations strongly adhering to the intrinsicallyconductive polymer. This object is achieved by bringing an aqueouscolloidal dispersion of the intrinsically conductive polymer intocontact with a cation exchange resin and/or an anion exchange resin.This step can be carried out at 0° C. to 100° C., preferably at 5° C. to50° C. in consideration of the heat resistance and workability of theion exchange resin.

The cation exchange resin is not specifically restricted; it may beselected from commercial ones. A preferred example is hydrogen formstrong acid cation exchange resin, which is available under a trade nameof Amberlite IR-120B (from Organo). The anion exchange resin is notspecifically restricted either; it may be selected from commercial ones.A preferred example is hydroxyl group form strong base anion exchangeresin, which is available under a trade name of Amberlite IRA-410 (fromOrgano).

There are not specific restrictions on the method of bringing an aqueouscolloidal dispersion of the intrinsically conductive polymer intocontact with an ion exchange resin so long as the method can clear theintrinsically conductive polymer of cations adhering thereto. Removal ofcations is accomplished most effectively by the passing of liquid, thatis, by passing an aqueous colloidal dispersion of the intrinsicallyconductive polymer through a column filled with an ion exchange resin. Aspace velocity of about 1 to 10 per hour is adequate for this process.

Deionization is accomplished more effectively by employing both a cationexchange resin and an anion exchange resin than by employing only eitherof them. The order of contact with the two ion exchange resins is notspecifically restricted; however, it is desirable to make contact with acation exchange resin and then with an anion exchange resin because theaqueous colloidal dispersion increases in pH after anion exchange, withthe result that the intrinsically conductive polymer loses its dopantand decreases in conductivity.

The aqueous colloidal dispersion may contain about 0.001 to 10.0 wt % ofsolids when it undergoes deionization by means of ion exchange. However,the solid contents should preferably be about 0.05 to 5.0 wt % in viewof workability and productivity. In the case where the intrinsicallyconductive polymer is polyaniline, a mixture of polyaniline andpolythiophen or a copolymer thereof, the aqueous colloidal dispersionshould preferably have a pH value lower than 3 and an electricconductivity value lower than 5 mS/cm if it contains 1 wt % of solids.

It will be noted that the aqueous colloidal dispersion of anintrinsically conductive polymer, which has been deionized according toan ion exchange method, has the possibility that dopants necessary forkeeping conductivity are also removed, so that dopants may besupplemented after the deionizating treatment in some cases.

[Filtration Step]

The aqueous colloidal dispersion can be purified more if deionization(mentioned above) is preceded by ultrafiltration which effectivelyremoves free ions and excess dopant.

Ultrafiltration may be accomplished by using an ultrafiltration membraneor tube. The temperature for this procedure should preferably be about 0to 80° C., which is low enough for adequate ultrafiltration. Continuousor intermittent water supply during ultrafiltration is desirable toensure complete removal of free ions and excess dopant.

The ultrafiltration membrane or tube used in this step is notspecifically restricted in its molecular weight cutoff. The one with amolecular weight cutoff of 10,000 to 200,000 is desirable.Ultrafiltration with an excessively small molecular weight cutoff takesa very long time; ultrafiltration with an excessively large molecularweight cutoff also permits the intrinsically conductive polymer toescape.

Ultrafiltration should preferably be performed on an aqueous colloidaldispersion of an intrinsically conductive polymer containing about 0.001to 10.0 wt % of solids. Concentrations of about 0.05 to 5.0 wt % is moredesirable for good workability and productivity. Duration of filtrationis usually 1 to 50 hours, although not specifically restricted.

In the case where the intrinsically conductive polymer is polyaniline,the aqueous colloidal dispersion should preferably have a pH value lowerthan 3 if it contains 3 wt % of solids. In the case where theintrinsically conductive polymer is poly-3,4-ethylenedioxythiophene, theaqueous colloidal dispersion should preferably have a pH value lowerthan 3 if it contains 1.3 wt % of solids.

The aqueous colloidal dispersion of intrinsically conductive polymerdecreases in pH value after it has undergone ultrafiltration. It furtherdecreases in pH value after it has undergone deionization. Its pH valueshould preferably be lower than 2 if the intrinsically conductivepolymer is polyaniline and the solid contents is 3 wt %, and lower than2.5 if the intrinsically conductive polymer ispoly-3,4-ethylenedioxythiophene and the content of solids is 1 wt %.

[Solvent Substitution Step]

The aqueous colloidal dispersion of intrinsically conductive polymer,which has undergone deionization as mentioned above, subsequentlyundergoes solvent substitution, so that it is converted into an organicsolvent dispersion of an intrinsically conductive polymer.

Solvent substitution may be accomplished in any manner; for example, byremoving water from the aqueous colloidal dispersion under normalpressure or reduced pressure and then adding an organic solvent to it,by adding an organic solvent to the aqueous colloidal dispersion andthen removing water from it under normal pressure or reduced pressure,or by removing water while adding by slow degrees an organic solvent tothe aqueous colloidal dispersion under normal pressure or reducedpressure. The last method is most desirable to minimize the watercontent in the organic solvent dispersion of intrinsically conductivepolymer.

Organic solvents to be used for solvent substitution are notspecifically restricted so far as organic solvents other thanN-methylpyrrole and dimethylsulfoxide used as an additive are used. Inorder to efficiently remove water, hydrophilic organic solvents arepreferred. The hydrophilic organic solvents include, for example,alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol,1-hexanol, 1-octanol and the like, ketones such as acetone, methyl ethylketone, diethyl ketone and the like, amides such as formamide,N-methylacetamide, and the like, ethers such as diethyl ether and thelike, and esters such as methyl acetate, ethyl acetate and the like.

Of these, alcohols having 1 to 3 carbon atoms such as methanol, ethanol,1-propanol, 2-propanol and the like are preferred.

Especially, when taking the convenience in practical application intoaccount, an organic solvent having a boiling point of 80° C. or lower isfavorable.

It will be noted that these organic solvents may be used singly or incombination of two or more.

Solvent substitution should be carried out at an adequate temperaturewhich depends on the boiling point of the solvent to be used. It shouldproceed under reduced pressure at as low a temperature as possible sothat it will not deteriorate the intrinsically conductive polymer. Thedispersion which undergoes solvent substitution should preferablycontain about 0.05 to 10.0 wt % of solids for good workability andproductivity. If water is to be removed while an organic solvent isbeing added slowly, it is desirable to add the organic solvent at anadequate rate which keens the solid contents in the above-mentionedrange.

[Additive-Treating Step]

The invention further includes a step of adding a compound capable offurther improving conductivity to the organic solvent dispersion of anintrinsically conductive polymer obtained by the method mentioned above.

The compound capable of improving conductivity includesN-methylpyrrolidone, dimethylsulfoxide, ethylene glycol,N,N-dimethylacetamide, dimethylformamide, tetrahydrofuran, acetonitrileand the like. In view of the effect of improving conductivity,N-methylpyrrolidone and dimethylsulfoxide are preferred.

The amount of the compound for improving conductivity is preferably from0.01 to 5.00% (W/V), more preferably from 0.01 to 0.99% (W/V) relativeto the total volume of the organic solvent dispersion.

A series of procedures mentioned above yields an organic solventdispersion of an intrinsically conductive polymer which has a greatlyreduced water content less than 2%, even less than 1%, which has neverbeen attained by conventional processes.

After the above-mentioned steps, the resulting organic solventdispersion of an intrinsically conductive polymer should preferablyundergo wet milling to improve its dispersibility. Wet milling may beaccomplished by using any of sand grinder, ball mill, disper, colloidmill, ultrasonic homogenizer, and high-pressure homogenizer. The lasttwo are desirable for easy handling, short processing time, and gooddispersibility.

The organic solvent dispersion of an intrinsically conductive polymerwhich is obtained by the method of the invention and whose water contentis small can satisfactorily show characteristics of the intrinsicallyconductive polymer with respect to the electric conductivity and heatray (infrared ray) absorbability. In addition, because of the type ofadditive, the dispersion can be appropriately employed for manyapplications as an electrode material, an antistatic agent, a UVabsorber, a heat ray absorber, an electromagnetic absorber, a sensor, anelectrolyte for electrolytic capacitor, an electrode for secondary celland the like.

EXAMPLES

The invention will be described below in more detail with reference toExamples and Comparative Examples, which are not intended to restrictthe scope thereof. Physical properties in the examples were measured asfollows.

[1] pH

Measured at 25° C. by using a digital pH meter “HM-50V”, from Toa DempaKogyo.

[2] Electrical Conductivity

Measured at 25° C. by using a conductivity meter “CM-30G”, from ToaDempa Kogyo.

[3] Surface Resistivity

Measured by using “Loresta IP TCP-T250”, from Mitsubishi Chemical.

[4] Viscosity

Measured at 25° C. by using a rotational viscometer, EL type, fromTOKIMEC.

[5] Particle Diameter

Measured by using “Microtrack UPA250”, from Microtrack.

[6] Water Content

Measured by using a Karl Fisher moisture meter “MKA-3p”, from KyotoDenshi Kogyo.

Example 1

A thousand grams of an aqueous colloidal dispersion 6903-104-004 (madeby ORMECON GmbH, with a solid content of 1.3 wt %, pH 2.0, and anelectric conductivity of 3.9 mS/cm) of an intrinsically conductivepolymer containing doped polyaniline was passed (at a space velocity perhour of 7) through a column (column diameter of 45 mm) packed with 250ml of a hydrogen form strong acid cation exchange resin (IR-120B, fromOrgano), thereby obtaining 1,506 g of a cation-exchanged, aqueouscolloidal dispersion. The thus obtained cation-exchanged, aqueouscolloidal dispersion had pH 2.1, an electric conductivity of 2.6 mS/cmand a solid content of 0.9 wt %.

The water medium in the cation-exchanged, aqueous colloidal dispersionwas substituted with methanol by a method wherein 22.5 liters ofmethanol was gradually added to the dispersion in an evaporator (anin-vessel pressure of 60 Torr., and an external heater temperature of75° C.) to remove water, thereby obtaining 864 g of a methanoldispersion of the intrinsically conductive polymer (during the solventsubstitution, the solid content was kept at 0.5 to 3 wt %). Then, 334 gof methanol and 9.6 g of N-methylpyrrolidone (0.7 w/v % relative to themethanol dispersion) were added to 860 g of the methanol dispersion toadjust the solid content to 1 wt %. The dispersion was treated with anultrasonic homogenizer (UIP 2000, made by Dr. Hielscher GmbH) to obtain1,114 g of a methanol dispersion of the intrinsically conductivepolymer. The thus obtained methanol dispersion had a solid content of1.1 wt %, a viscosity of 2.4 mPa·s, a water content of 0.9 wt %, and aparticle diameter of 58 nm. This methanol dispersion was applied onto aglass sheet with an applicator (in a wet thickness of 25 μm) and driedat 110° C. for 10 minutes to obtain a film having a surface resistivityof 1.8×10³ Ω/□.

It will be noted that the surface resistivity in the case where noN-methylpyrrolidone was added was at 3.5×10³ Ω/□.

Example 2

A thousand grams of an aqueous colloidal dispersion 6903-104-005 (madeby ORMECON, with a solid content of 1.2 wt %, pH 1.9 and an electricconductivity of 4.2 mS/cm) of an intrinsically conductive polymercontaining doped polyaniline was passed through a column (with a columndiameter of 45 mm) packed with 250 ml of a hydrogen form strong acidcation exchange resin (IR-120B, from Organo) at 25° C. (at a spacevelocity per hour of 7) to obtain 1,389 g of a cation-exchanged, aqueouscolloidal dispersion. The resulting cation-exchanged, aqueous colloidaldispersion had pH 2.1, an electric conductivity of 3.1 mS/cm, and asolid content of 0.9 wt %.

The water medium in the cation-exchanged aqueous colloidal dispersionwas substituted with methanol by a method wherein 22 liters of methanolwas gradually added to the dispersion in an evaporator (under anin-vessel pressure of 60 Torr., at an outer heater temperature of 75°C.) to remove water, thereby obtaining 860 g of a methanol dispersion ofthe intrinsically conductive polymer (during the solvent substitution,the solid content was kept at 0.5 to 3 wt %). Then, 438 g of methanoland 8.1 g of N-methylpyrrolidone (0.6 w/v % relative to the methanoldispersion) were added to 854 g of the methanol dispersion to adjust thesolid content to 1 wt %, the dispersion was treated with an ultrasonichomogenizer (UIP2000, made by Dr. Hielscher) to obtain 1,236 g of amethanol dispersion of the intrinsically conductive polymer. The thusobtained methanol dispersion had a solid content of 1.0 wt %, aviscosity of 2.5 mPa·s, a water content of 0.8 wt % and a particlediameter of 29 nm. The methanol dispersion was applied onto a glasssheet with an applicator (in a wet thickness of 25 μm) and dried at 110°C. for 10 minutes to obtain a film having a surface resistivity of2.3×10³ Ω/□.

It will be noted that the surface resistivity in the case where noN-methylpyrroliione was added was at 6.6×10³ Ω/□.

Example 3

Eight hundred grams of an aqueous colloidal dispersion 6903-109-003(made by ORMECON GmbH, with a solid content of 1.6 wt %, pH 1.8 and anelectric conductivity of 6.4 mS/cm) of an intrinsically conductivepolymer containing doped polyaniline was passed through a column (with acolumn diameter of 45 mm) packed with 250 ml of a hydrogen form strongacid cation exchange resin (IR-120B, from Organo) at 25° C. (at a spacevelocity per hour of 7) to obtain 1,137 g of a cation-exchanged, aqueouscolloidal dispersion. The resulting cation exchanged, aqueous colloidaldispersion had pH 1.9, an electric conductivity of 4.9 mS/cm, and asolid content of 1.1 wt %.

The water medium in the cation-exchanged aqueous colloidal dispersionwas substituted with methylated ethanol by a method wherein 11 liters ofmethylated ethanol was gradually added to the dispersion in anevaporator (under an in-vessel pressure of 60 Torr., at an outer heatertemperature of 75° C.) to remove water, thereby obtaining 713 g of amethylated ethanol dispersion of the intrinsically conductive polymer(during the solvent substitution, the solid content was kept at 0.5 to 3wt %). Then, 529 g of methylated ethanol and 9.9 g of dimethylsulfoxide((0.6 w/v %) relative to the methylated ethanol dispersion) were addedto 705 g of the methylated ethanol dispersion to adjust the solidcontent to 1 wt %. The dispersion was treated with an ultrasonichomogenizer (UIP2000, made by Dr. Hielscher) to obtain 1,171 g of amethylated ethanol dispersion of the intrinsically conductive polymer.The thus obtained methylated ethanol dispersion had a solid content of1.0 wt %, a viscosity of 20 mPa·s, a water content of 0.9 wt % and aparticle diameter of 25 nm. The methylated ethanol dispersion wasapplied onto a glass sheet with an applicator (in a wet thickness of 25μm) and dried at 110° C. for 10 minutes to obtain a film having asurface resistivity of 6.0×10² Ω/□.

Comparative Example 1

Ten grams of a hydrogen form strong acid cation exchange resin (IR-120B,from Organo) and 10 g of a hydroxyl group form strong base anionexchange resin (IRA-410, from Organo) were added to 215 g of an aqueouscolloidal dispersion Baytron-P (made by Bayer AG, with a solid contentof 1.3 wt %, pH 1.7 and a conductivity of 71 mS/cm) ofpoly-3,4-ethylenedioxythiphene (PEDOT), followed by agitation for 8hours. The respective ion exchangers were removed by filtration toobtain 206 g of a cation-anion exchanged PEDOT aqueous colloidaldispersion. The thus obtained cation-exchanged PEDOT aqueous colloidaldispersion had pH 2.0, and a conductivity of 6.0 mS/cm.

An attempt of substituting the water medium in the obtained cation-anionexchanged PEDOT aqueous colloidal dispersion with methanol was made by amethod wherein 9.0 liters of methanol was gradually added to thedispersion in an evaporator (under an in-vessel pressure of 60 Torr., atan outer heater temperature of 75° C.) to remove water. During thesolvent substitution, the solid content was kept at 0.5 to 2.0 wt %.However, occurrence of a coagulation in a large amount and two-phaseseparation were observed, so that no uniform methanol dispersion ofPEDOT could not be obtained.

1. A method for producing an organic solvent dispersion of anintrinsically conductive polymer, which comprises: a deionizing step ofdeionizing an aqueous colloidal dispersion of an intrinsicallyconductive polymer by the passing of liquid, thereby clearing theintrinsically conductive polymer of cations adhering thereto; a solventsubstitution step of substituting water in the aqueous colloidaldispersion with an organic solvent except for N-methylpyrrolidone anddimethylsulfoxide after the deionizing step; and an additive-treatingstep of adding N-methylpyrrolidone or dimethylsulfoxide to thedispersion obtained by the solvent substitution step.
 2. The method forproducing an organic solvent dispersion of an intrinsically conductivepolymer of claim 1, wherein an amount of the N-methylpyrrolidone ordimethylsulfoxide ranges from 0.01 to 5.00% (W/V) relative to the totalvolume of the organic solvent dispersion.
 3. The method for producing anorganic solvent dispersion of an intrinsically conductive polymer ofclaim 2, wherein the amount of the N-methylpyrrolidone ordimethylsulfoxide ranges from 0.01 to 0.99% (W/V) relative to the totalvolume of the organic solvent dispersion.
 4. The method for producing anorganic solvent dispersion of an intrinsically conductive polymer ofclaim 1, wherein the deionizing step is accomplished by ion exchange. 5.The method for producing an organic solvent dispersion of anintrinsically conductive polymer of claim 1, further comprising afiltration step of subjecting the aqueous colloidal dispersion of anintrinsically conductive polymer to ultrafiltration before thedeionizing step.
 6. The method for producing an organic solventdispersion of an intrinsically conductive polymer of claim 1, whereinthe solvent substitution step is accomplished in such a way as to keep asolid contents in a range of 0.05 to 10.0 wt %.
 7. The method forproducing an organic solvent dispersion of an intrinsically conductivepolymer of claim 1, wherein the solvent substitution step isaccomplished in such a way as to reduce a water content below 1%.
 8. Themethod for producing an organic solvent dispersion of an intrinsicallyconductive polymer of claim 1, wherein the solvent substitution step isaccomplished by slowly adding the organic solvent to the aqueouscolloidal dispersion, thereby removing water.
 9. The method forproducing an organic solvent dispersion of an intrinsically conductivepolymer of claim 1, wherein the organic solvent is an alcohol having 1to 3 carbon atoms.
 10. The method for producing an organic solventdispersion of an intrinsically conductive polymer of claim 1, whereinthe organic solvent has a boiling point of not higher than 80° C. 11.The method for producing an organic solvent dispersion of anintrinsically conductive polymer of claim 1, wherein the intrinsicallyconductive polymer contains at least an aniline unit.
 12. The method forproducing an organic solvent dispersion of an intrinsically conductivepolymer of claim 1, wherein the intrinsically conductive polymer isdoped polyaniline, doped polythiophene, a mixture thereof or a copolymerthereof.
 13. An organic solvent dispersion of an intrinsicallyconductive polymer obtained by the method defined in claim
 1. 14. Adispersion of an intrinsically conductive polymer in an organic solventexcept for N-methylpyrrolidone and dimethylsulfoxide, which includingN-methylpyrrolidone or dimethylsulfoxide, a water content being lessthan 1%.
 15. The dispersion of claim 14, wherein a content of theN-methylpyrrolidone or dimethylsulfoxide ranges from 0.01 to 5.00% (W/V)relative to the total volume of the organic solvent dispersion.
 16. Thedispersion of claim 15, wherein the content of the N-methylpyrrolidoneor dimethylsulfoxide ranges from 0.01 to 0.99% (W/V) relative to thetotal volume of the organic solvent dispersion.
 17. The dispersion ofclaim 14, wherein the organic solvent is an alcohol having 1 to 3 carbonatoms.
 18. The dispersion of claim 14, wherein the organic solvent has aboiling point of not higher than 80° C.
 19. The dispersion of claim 14,wherein the intrinsically conductive polymer has at least an anilineunit.
 20. The dispersion of claim 14, wherein the intrinsicallyconductive polymer is a doped polyaniline, a doped polythiophene, amixture thereof or a copolymer thereof.
 21. The dispersion of claim 14,wherein the conductive polymer is a mixture of a doped polyaniline and adoped polythiophene, or a copolymer thereof.
 22. The dispersion of claim14, wherein the intrinsically conductive polymer is a mixture of a dopedpolyaniline and a doped polythiophene.